Studies of substance use, abuse and dependence suggest that adolescence is a time of increased risk for substance addiction. Poor judgment and decision making during this period of development may lead to suboptimal choices to use and ultimately abuse substances. This application examines the development of cognitive and neural processes underlying decision-making that may place adolescents at greater risk for substance abuse. We will test specific hypotheses regarding the development of decision-making during adolescence and how these processes are biased by reward and emotion manipulations as well as by risky and impulsive tendencies. We will use a modified version of a go/no go task and a two-choice decision task across all four specific aims, manipulating the reward or emotional significance of choices to be made. Formal models of reinforcement learning and principles of decision making together with functional neuroimaging will be used to constrain our hypotheses about developmental and individual behavioral differences in decision making. This proposed program of research will inform 10 of the 13 topic areas this RFA listed as exemplar areas of research. These studies will lay the critical groundwork, both scientific and methodologic, in mapping the development of decision making in adolescents, for subsequent studies on substance use and abuse in adolescents. The proposed studies are in response to RFA # DA-04-009 Behavioral and Cognitive Processes Related to Adolescent Drug Abuse.